Vacuum machines used for industrial or commercial applications are well-known in the art. Typically, such industrial machines or "shop" vacuums have a large-capacity reservoir in the form of a top-filling tank or drum. For dry applications, the vacuum motor may be mounted to the underside of a lid which is received on and seals the tank. For applications where there is no collection bag used, the intake to the reservoir may be located in a side wall of the reservoir. In machines of this type, the intake of the reservoir typically is mounted as high as possible on the side wall of the reservoir to increase the storage capacity of the reservoir. However, such location for the intake precludes use of a collection bag in the form of a sack (i.e., having a completely open top) because if the top edge of "mouth" of the bag is folded over the top edge of the reservoir, the vacuum intake would be covered by the bag.
Thus, when it is desired to use a bag for collection of materials, a special connecting conduit may be used to connect the intake with the bag, in which case the storage capacity of the bag is necessarily less than the capacity of the reservoir.
As the toxic nature of asbestos became generally well-known, there arose a need for vacuum machines to collect asbestos debris (or other toxic waste materials) without dischaging the toxins in the exhaust of the vacuum motor. This required the development of several filtering stages. Typically, in a case of a dry vacuum machine, there might be a cloth or paper bag pre-filter and perhaps other stages of filtering. Usually, however, the final filter is a High Efficiency Particulate Air (or "HEPA" for short) filter. The incorporation of such pre-filter and HEPA filter stages made an otherwise conventional vacuum machine (sometimes called a "critical filter vacuum") useful in collecting toxic waste; but the inclusion of the additional filters reduces the storage capacity of the reservoir.
In an effort to increase storage capacity, debris collected by the machine and to accommodate it to "wet" applications, at least one commercial machine employs an extension or adapter wall for the reservoir which mounts on top of the reservoir and extends upwardly to accommodate and house the additional filter section. Thus, the filters do not extend into the reservoir which would diminish its capacity. In this type of machine, the conventional intake at the top of the normal reservoir is sealed, and a new intake is provided in the adapter, above the top edge of the reservoir. A collection bag could then be used without diminishing the storage capacity of the reservoir by clamping the top edge of the bag between the top edge of the reservoir and the bottom edge of the adapter.
To accommodate such a machine for both dry and wet applications, a cut off valve is provided in a location between the reservoir and the adapter, so that liquids are stored directly in the tank and the full storage capacity of the tank may be used to store liquids (at least up to the level of the intake).
However, for dry applications, this commercial machine requires a special connector conduit between the vacuum intake and a bag in the reservoir, thereby further reducing storage capacity for debris and rendering it inconvenient to change the bags.
Thus, there is a need to adapt industrial or commercial vacuum machines to critical filter vacuums for either wet or dry applications without diminishing the storage capacity of the reservoir and while permitting conventional top-fill collection bags to be used simply by folding the mouth of the bags over the top edge of the reservoir of the machine, rather than requiring special conduits or special types of bags in such applications.